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Medical Science Monitor Basic Research


eISSN: 1643-3750

A step towards the discrimination of beta-lactamase-producing clinical isolates of Enterobacteriaceae and Pseudomonas aeruginosa by MALDI-TOF mass spectrometry

Reiner Schaumann, Nicolas Knoop, Gelimer H. Genzel, Kevin Losensky, Christiane Rosenkranz, Catalina S. Stîngu, Wolfgang Schellenberger, Arne C. Rodloff, Klaus Eschrich

Med Sci Monit 2012; 18(9): MT71-77

DOI: 10.12659/MSM.883339

Available online: 2012-08-30

Published: 2012-08-30


Background:    Matrix-Assisted Laser-Desorption/Ionization Time of Flight Mass Spectrometry (MALDI-TOF MS) has already proven to be a powerful tool for species identification in microbiological laboratories. As adequate and rapid screening methods for antibiotic resistance are crucially needed, the present study investigated the discrimination potential of MALDI-TOF MS among extended-spectrum-beta-lactamase (ESBL) or metallo-beta-lactamases- (MBL) producing and the nonproducing strains of Escherichia coli (n=19), Klebsiella pneumoniae (n=19), and Pseudomonas aeruginosa (n=38), respectively.
    Material/Methods:    We used a MALDI-TOF MS protocol, usually applied for species identification, in order to integrate a screening method for beta-lactamases into the routine species identification workflow. The acquired spectra were analyzed by visual inspection, statistical similarity analysis and support vector machine (SVM) classification algorithms.
    Results:    Neither visual inspection nor mathematical similarity analysis allowed discrimination between spectra of beta-lactamase-producing and the nonproducing strains, but classification within a species by SVM-based algorithms could achieve a correct classification rate of up to 70%.
    Conclusions:    This shows that MALDI-TOF MS has definite potential to discriminate antibiotic-resistant strains due to ESBL and MBL production from nonproducing strains, but this performance is not yet sufficiently reliable for routine microbiological diagnostics.

Keywords: Species Specificity, Pseudomonas aeruginosa - isolation & purification, Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization - methods, Klebsiella pneumoniae - isolation & purification, Escherichia coli - isolation & purification, Drug Resistance, Bacterial - genetics, Cluster Analysis, Bacterial Infections - microbiology, beta-Lactamases - metabolism